Project memo AN 02.12.56
Active front-end-converter, model verifications and design challenges
SINTEF Energy Research
1

Objectives
„ Verify simulation model against measurement on laboratory set-up.
„ Summarize challenges related to active front-end converters that need further attention
„ NOTE: The model is intended for investigation of phenomena in the frequency range from DC to well above switching frequency (not including radio frequency phenomena)
SINTEF Energy Research
2

Principal drawing of power circuit
Optionally connected to
DC-source /
DC-load u
DC
+ i a i b i c i a,mains
+ + + u a u b
u c
Connected to AC-grid
SINTEF Energy Research
3

Case description
„ DC-link voltage reference: 400 V
„ AC-network line voltage: 230V rms
„ Reactive current reference: Initially +35A peak and then stepped to –35A peak (momentarily reversal of reactive power flow from lag to lead )
„ No other load or source connected to the DC-link. Only a small active current component is needed to cover the power losses in the converter.
SINTEF Energy Research
4

Illustration of the verification case
Untitled no name
I mains R
+0.2
VR
+0.12
+0.04
-0.04
-0.12
0.2112
0.2274
Time (sec)
0.2436
Filter capacitor voltage
AC grid current
0.2598
SINTEF Energy Research
0.276
5

Capacitor voltage
Simulated
Measured
SINTEF Energy Research
6

Converter current and current reference
Simulated
Measured
Simulated refernce
SINTEF Energy Research
7

Zoom of previous slide
Simulated
Measured
Simulated refernce
SINTEF Energy Research
8

Conclusions model verification
„ Good agreement between simulated and measured quantities
„ The converter model is sufficient accurate for its intended use for future investigation and improvement of active front-end converters
„ NOTE: Intended use is the frequency range from DC quantities up to well above switching frequency (not the radio frequency range)
SINTEF Energy Research
9

Challenges that need further attention
„ Oscillations between supply network inductance and ACside filter capacitor.
„ Consequences of AC-side filter capacitor working as a filter for other components connected to the AC-side network (typically diode rectifiers).
„ Design of AC-side filter.
„ Common mode interference (to AC-network)
„ Possible dangerous constant power load behaviour.
„ Converter response to transients and failures in ACnetwork
„ Active damping of filter oscillations
„ Optimal use of measurements
SINTEF Energy Research
10

Illustration of challenges
Untitled no name
VR I mains R
+0.3
+0.18
+0.06
-0.06
-0.18
0.0794
0.0888
Time (sec)
0.0982
0.1076
0.117
Simulated filter capacitor voltage (kV / black / squares) and AC-network current (kA, red /triangles). A single-phase peak diode rectifier injects harmonics that flows into the AC-filter of the active front-end converter
SINTEF Energy Research
11

PROJECT MEMO
MEMO CONCERNS
SINTEF Energy Research
Active front-end-converter, model verifications and design challenges
Trondheim,
NORWAY
Reception:
Telephone:
Sem Sælands vei 11
+47 73 59 72 00
DISTRIBUTION
Magnar Hernes
Telefax: +47 73 59 72 50 Kjell Ljøkelsøy
Nils Arild Ringheim www.energy.sintef.no
Olve Mo
Enterprise No.:
NO 939 350 675 MVA
AN NO. CLASSIFICATION REVIEWED BY
AN021256 Unrestricted Magnar Hernes
ELECTRONIC FILE CODE AUTHOR(S) DATE
PROJECT NO.
12X127 Olve.Mo@energy.sintef.no
NO. OF PAGES
22
DIVISION LOCATION
Energy Systems Sem Sælands Vei 11 +47 73 59 72 50
This memo present results of the Strategic Institute Programme (SIP) “Power electronics and energy storage technologies for cost- and energy efficient power systems” funded by The
Research Council of Norway.
A simulation model of the active front-end converter prototype has been established and has been documented in [1]. Simulated behaviour has now been compared to measurements taken on the laboratory prototype. These comparisons are presented in this memo as a verification of the simulation model.
The agreement between simulated and measured quantities is considered to be good. Proposals for further model refinement are included, although the model is already sufficient for its intended use in future investigation and improvement of active front-end converters. This includes effect in the frequency range from DC quantities up to well above switching frequency. The model is however not developed and suited for analysis of phenomena in the radio frequency range.
This memo also outlines challenges that need further attention:
·
·
·
·
·
·
Oscillations between supply network inductance and AC-side filter capacitor.
Consequences of AC-side filter capacitor working as a filter for other components connected to the AC-side network (typically diode rectifiers).
Design of AC-side filter.
Common mode interference (to AC-network)
Possible problematic constant power load behaviour.
Converter response to transients and failures in AC-network
·
·
Active damping of filter oscillations
Optimal use of measurements
12X127 AN021256

2
TABLE OF CONTENTS
Page
1 THE SIMULATION MODEL.......................................................................................... 3
2 MEASUREMENTS ON THE PROTOTYPE .................................................................. 4
2.1 The converter prototype ........................................................................................ 4
3 COMPARISON OF MEASURED AND SIMULATED RESULTS ............................... 5
3.1 Illustration of the selected case ............................................................................. 5
3.2 Simulated versus measured quantities .................................................................. 6
4 DISCUSSION AND CONLUSIONS ON MODEL VERIFICATION .......................... 10
4.1 Compliance between simulation and measurement ............................................ 10
4.2 Likely explanations to observed deviations ........................................................ 10
4.3 Conclusion........................................................................................................... 10
INVESTIGATION ...................................................................................... 11
5.1 Resonance between AC network and AC filter capacitor................................... 11
5.2 Oscillations due to other harmonic sources ........................................................ 12 design................................................................................................... 13 damping ................................................................................................... 13
5.5 Common mode interference................................................................................ 13
5.6 DC-link voltage controller bandwidth ................................................................ 14
5.7 Response to failure and transients in AC-network.............................................. 14
5.8 Reliability and cost of measurements ................................................................. 14
6 REFERENCES ............................................................................................................... 15
APPENDIX A EMTDC/PSCAD MODEL ................................................................... 16
12X127 AN021256